This invention relates to a load cell assembly and more particularly to a mounting and holding system for the load cell, a load cell holding member and also a method of installing the same. The invention is particularly adapted for use in semi trucks and trailers.
Load cells are commonly used on semi-trucks and trailers to determine the weight of the load being carried. Load cells commonly function by utilizing an internal strain gage that measures deflection or sheer. Because the modulus of elasticity of a load cell is constant the amount of strain can be calibrated to determine the force upon the cell. The load cell is supported at its two end locations with force from the structure to which it is mounted acting upwardly on the load cell at each end location. The force exerted by the load to be measured is directed downwardly at the center portion of the load cell. This force stresses the load cell in a manner that the strain gages provide an output corresponding to the weight of the load being measured. For the load cells to function properly they must be rigidly mounted to a base structure, such as the frame of the semi truck or trailer.
A semi-truck generally has a frame that basically comprises two C-channel beams where the channel flanges are facing towards each other, separated by a lateral distance of approximately 34 inches, and they extend from the rear to the front of the truck or trailer. The C-channel beams each have an upper and a lower substantially level flanges and an outer substantially vertical web. The outer webs are on the outer exposed portion of the frame. The load cells extend longitudinally and there are at least two load cells per truck and trailer, each rigidly attached to its related C-channel member. A load bearing member spans the lateral distance between the each pair of cells and is connected to the center portion of each load cell.
The connection of the load cell holding means to the upper flange of the C-channel portion of the frame must be a rigid connection. Traditionally the load cells are attached by first bolting a lower leg of a structural angle to the vertical web of a C-channel member. The structural angle is mounted longitudinally with the C-channel and has a length which is longer than the load cell. The structural angle is bolted at several locations to the central area of the vertical web of the C-channel. In one prior art arrangement, the structural angle is configured so that upper horizontal leg of the structural angle is positioned directly on top of the upper flange of the C-channel and the lower leg of the structural angle is bolted at several locations to the more central area of the vertical web of the C-channel.
Traditionally there are provided load cell holding members that are welded on top of the upper leg of the structural angle. The process generally consists of retrieving an expendable load cell as an assembly fixture and bolting it down to the load cell holding members. Then the load cell holding members are welded down to the upper portion of the structural angle. This procedure is a time consuming and there are various problems such as the welds being subject to failure by fatigue, warpage and other problems.